Posted
by
samzenpus
on Wednesday January 04, 2006 @11:36PM
from the stuff-is-moving-but-barely dept.

IZ Reloaded writes "Any would be travellers to Pluto should bring extra winter gear. The new temperature on Pluto according to scientists is 43 degrees Kelvin. That's 10 degrees Kelvin colder than expected. From CNN: "Astronomers think Pluto's colder than expected temperature reading involves interactions between nitrogen ice on the planet's surface and the nitrogen gas that makes up its atmosphere...Pluto is a dynamic example of what we might call an anti-greenhouse effect...""

I don't understand why it would require so much more insulation. Isn't heat transfer proportional to the difference in temperature of each side? So if you wanted to maintain your equipment at 0c, that's 273K-43K = 230 vs 273K-53K= 220. The heat transfer of the material is a constant, so 230/220 = 1.045, so about 4.5% thicker insulation.

Batteries don't tend to work very well at all at 43K. Since batteries are chemical devices the chemical reactions happen MUCH slower (if at all) at such a low temperature.

I don't know the effects of cold on normal solid state electronics, but I wouldn't have a problem believing that some components aren't going to work normally at 43K. It's not as if the parts manufacturer tests them at these extreme temperatures.

That is just one of the reasons you don't use batteries far from the sun. RTG's generate a constant source of heat and electricity for years due to radioactice decay. You could up the anti with a full scale nuclear reactor but nasa would be hard pressed to sneak that out of the gravity well. The only other option is to beam energy there but that is a problem becuase it's hard the amim the attena. Nuclear power is really the only way to go for deep space travle.

Well, from what I know the reason that RTG generators are used is because of the extremely low light levels so far from the sun, not cold. The Mars rovers for instance use solar panels with batteries and heaters. I'd bet batteries+solar panel+heaters is a LOT cheaper than an RTG.

But you're right, on a mission to pluto they'd have to use an RTG for power, so chemical batteries wouldn't be needed. I hadn't thought of the low light levels. But, the original point is that a heat source is important because electronics don't work the same at such extremely low temperatures.

everything had frozen solid and the thermometer registered -150 C. Success. Then the monitor started to flash strange images. Pressing keys on the keyboard produced random characters on the screen. "In other words," Tranquilino says, "the motherboard wa

Actually, the electronics needs to work also during the trip, where the temperature is about 2.7 K.

Not really. The temperature of the heliosphere is actually rather high -- don't remember exactly offhand, but it's higher than the interstellar medium, which is somewhere around 7000K (give or take a couple thousand Kelvins). It's just that it stores almost no heat, since there's so little matter. (This is slightly sloppy wording, but close enough.) The upshot is that there is almost no heat conduction in either direction and almost all heat transfer occurs by blackbody radiation, which is amazingly inefficient. Even though Pluto doesn't have an atmosphere, touching the surface changes this entirely by providing a material to transfer heat to -- that's why a probe landing on Pluto would need a lot of insulation that a non-landing probe (e.g., V'ger) wouldn't.

That's not the temperature of the interstellar medium, it's the temperature of the cosmic background radiation -- they are completely different. I can see where the confusion could come from, though. Short version:

Cosmic Microwave Background: The residual heat of the big bang, redshifted (cooled) by ~13 billion years of expansion. This temperature is given in terms of the Stefan-Boltzmann relation (blackbody temperature), and basically represents the average temperature of the whole universe, including the vast, cold, empty intergalactic regions.

Interstellar Medium: A very diffuse (though still dense compared to the intergalactic regions) cloud of ionized gas filling the whole galaxy. These ionized particles move around very quickly, i.e., they're very hot (Maxwell-Boltzmann distribution). 7000K +/- 2000K according to this synopsis [mit.edu], at least for regions near the heliosphere.

Heliosphere: The gaseous bubble surrounding the sun out to about 100AU (Voyager 1 hit the termination shock where it meets the ISM at 94AU). It's hotter and denser than the interstellar medium, and it's where any space probe we launch would be travelling. Of course, since there is so little gas in even the heliosphere (its pressure would be considered a hard vacuum on Earth), these temperatures have very little effect on any spacecraft.

It's interesting because it's an effect they haven't seen before. An atmosphere actually helping to cool a planet is something new and pretty amazing. It seems to act like a giant evaporative cooler. The more that's understood about the physics of known planets the more accurate the information will be that can be gleaned from distant planets. Ten degrees may not seem like much but it's an important piece of the overall puzzle. It also means that Pluto is a lot more active and more interesting than people h

I just love the headline. Tourists dissappointed. Pluto falls short of vacationer's expectations.

Man on Pluto: "It's cold."

"It's not what we expected," said Mrs. White, mother of four, "We thought it'd be much milder than this. We haven't been able to go out all holiday and the kids have been bored. It was either this or Disney and the kids were all excited to get to see Pluto. We didn't think it'd be like this."

Mr. White says he intends to pursue compensation from NASA and other astronomic research orga

I think we need more information about this family here : is Mr White Mrs White's husband ? Why is he only the father of three while his wife is mother of four ? Perhaps Mrs White had one child from someone else, for instance in a previous marriage ?

To be even more pedantic than you, the difference of 10 degrees is actually correct (if they didn't write the Kelvin) because a difference of 10 Kelvin is identically a difference of 10 Degrees Centigrade.

Lord Kelvin has a son who inherits the title. He goes to Cambridge and takes his first degree in Natural Sciences and gets a First, while still managing to play Rugby. Then he goes to Oxford to do his BSc, and then goes back to Cambridge where he does a brilliant PhD while turning out part time for the England cricket team. At which point he has a nervous breakdown from all the work. As part of his recovery program he is found a nice quiet job working as a bus conductor (NB only older UK residents will understand this.)
One day two Girton girls are on his bus and one remarks his age and physique, turns to the other and murmurs "Super conductor". To which the other replies "Three degrees Kelvin."

As a result of the parent post, this joke is now officially demolished.

it's just the sort of place you'd need to run a few Pentium Extreme Edition systems.

But seriously, while researchers try to find exotic materials that exhibit room-temperature superconductivity, you could take more common materials and run them at insanely fast speeds out there. Of course, it would take a while to upload your code and data and download any processing results.......

What "dark side of Mercury?" It's been known for over twenty years that Mercury rotates in 2/3 of the time it takes to orbit the sun rather than having its day equal to its year. It's just that the best times to observe the planet by telescope come about 2/3 or 4/3 of an orbit apart. (Not sure which one, but in either case, the same side was always lit when we could observe it. It took doppler radar to find out what was really going on.)

Specifically, Mercury's day is 58.65 earth days long, while its year is 87.97 earth days long (source: NASA JPL [nasa.gov]).

From the same source, we see that Mercury's minimum temperature is about 100K (comfortably colder than liquid nitrogen). Obviously that would occur on the currently-dark side of the planet. So while there's no permanently-dark side of Mercury, there's certainly a cold dark part of mercury somewhere at any given point in time, and that coldest part is only about 50K away from Pluto's temp (presu

> it's just the sort of place you'd need to run a few Pentium Extreme Edition systems.

Microsoft has already launched a probe to harness the power of Pluto to cool the Xbox 360.

The White House, misreading the term "global warming", immediately denied that Pluto exists. After reading the article they retracted the statement and issued another, stating that they will investigate Pluto's "anti-warmification properties".

An investigation has been opened into just who Kelvin is, and why he's allowed to practice science without a degree.

On the other hand the thin nitrogen atmosphere on low gravity Pluto might cause each pin of the cpu to sprout multiple immense tornadoes in all directions, whirling across the entire hemisphere in an attempt to extract the heat which will in fact warm up the entire planet and possibly volatilize what you are standing on. On the other hand if you can bury the heat sink in solid ground you may be okay..

That's an interesting point. From the article, Pluto receives about 1/1000th as much sunlight as the Earth. From here http://www.powerfromthesun.net/chapter1/Chapter1.h tm [powerfromthesun.net] we see that the Earth receives 1367 watts per square meter, so we can assume that Pluto typically receives only 1.367 watts per square meter. Dumping the heat from a single P4EE into Pluto's surface could be pretty disruptive, hundreds of watts over a small surface area. The rush of nitrogen vapor would be like a bomb exploding.

But supposing one actually wanted to design a computer system that could operate on the surface of Pluto, I'm sure the heatsink design wouldn't be the worst problem. Just mount the CPU so that the heat-spreader is mated to the case, and sit the case on the planet surface. I don't know the thermal conductivity of frozen solid nitrogen, but I have a feeling it will be adequate. The heat of vaporization will take care of the rest.

so it says that Charon, Pluto's moon, is warmer than the planet. Since Charon is almost as big as Pluto, I am sure this new tidbit will add more to the deabte concerning what relation the two celestial bodies have with each other and how they came to be paired.

The correct use is "43 kelvins." Unlike degrees Celsius or degrees Fahrenheit (both adjectives), it is a noun, and the correct pluralization is kelvins.

I'm sure some newspaper will soon start running headlines about how Pluto is "23% colder than anticipated." In the real world, 10 K isn't that much, although it would be nice to know why our estimates are off. For reference, water freezes at 273.15 K, and the deepest darkest nook of outer space registers about 2.7 K, thanks to some background microwave radiation.

I hearby award you the pedantic nerd award of the day. Thanks for clearing up all the confusion that we all had with kelvin vs kelvins.

I think you've missed the point of the article. How it's "sensationalist" I can't understand at all. The point of the article was that astronomers have found something interesting. A planet that cools itself via "perspiration". Pretty neat if you ask me.

I was referring to the root post as sensational, not the article. "Much Colder..." and "degrees Kelvin" demonstrate a lack of grounding. TFA was actually pretty interesting (especially considering the source), but it describes a moderate effect akin to an "open system" air conditioner.

Of most importance: "The finding could apply to other planets in the solar system which have condensable atmospheres like Mars." IOW, it's another little piece in our understanding of the overall solar jigsaw puzzle.

I just re-read the article summary and I still don't see how anyone could think it's sensational. Much colder is a matter of perspective. It's colder than experimental error and what theory (based on reflectivity and light levels) can account for. That's enough to warrant some serious interest. Hell, when they first discovered high-temperature superconductors it was at 77K. It's all a matter of perspective and context. No one but a solid

Are you kidding? 10K isn't a lot at Earth temperatures. But it's a lot when you're that close to absolute zero. That "23%" (should be less somewhat less than 20%) is the way to think about it. It's analogous to the difference between 0 C and roughly -50 C. Namely, you need a substantial effect or error to be off by that much in temperature.

Heinlein's classic Have Space Suit, will Travel (which I will now call HSSWT) is one of Heinlein's last jouvenille novels to have its science become dated. The other novels had such quaint things as canals and martians on Mars, or a 200 where people had the ability to make synthetic gold, yet people still had to talk to a live bank teller to withdrawl money. HSSWT, until reasonably recently, had no such quaintness to it. However, (minor spoilers follow) there is a scene in the book where the hero has to

- the redhouse effect (red is complementary to green)
- the burnthouse effect (frost will "burn" plants in a greenhouse)
- the evergreenhouse effect (it is so cold that the plants are actually frozen green forever)
- the exgirlfriend effect (it's cold, and will never get warm; shameless plagiarizing another comment)

No. Pluto only has an atmosphere during its summer which it is currently in. (It is closer to the sun at 30AU than it will be again for a very long time) During the winter the atmosphere will give up it's heat and fall to the surface as solid nitrogen snow where it will sit for a couple hundred years until the sun once again turns it from solid to gas. But the surface will always stay at the same temperature. This is the same effect seen when you measure the temperature of water with ice cubes in it. The water will stay at 32 degrees until all the ice is gone even if you put a flame underneath. The added heat would merely make the ice melt faster rather than raise the water temperature.

Since Pluto has just passed through summer we can assume that the solid nitrogen lasts long enough to keep the surface cool for the entire warm period. Exactly the way the north polar cap only just lasts the summer on Earth.

Not worth the bother. Earth is already mostly a nitrogen atmosphere. Instead, heating (and cooling) is influenced by molecules that occur in small amounts (eg, carbon dioxide, sulfur dioxide, and methane).

This one is seen all the time. Analysis of user agents and IP addresses would be interesting. I wonder if I could attract the (presumed) robot by mirroring the posts. Might be a good way to set up a honeypot.